The color bar indicates temperature in units of 10^3 Kelvin. The Main Sequence and Giant Branch are indicated, as well as the primary stars of interest for the Trinity College Dublin (Ireland) Astrophysics Research Group (the Sun, Betelgeuse and EG Andromeda). As you can see, the Sun is quite an average star.

This diagram will be published in my PhD thesis (Higgins, 2012; submitted).